The genus Harttia Steindachner, 1877 belongs to the family Loricariidae, the most diversified of all catfish families with 673 valid and around 300 undescribed species. Stream water fish of the genus Harttia are found in the upper course of rivers on rocky and sandy bottoms. This monophyletic genus comprises at present 22 species (Rapp Py-Daniel and Olivei - ra, 2001) mainly distributed on the Guiana shield, the South East of Brazil in coastal rivers, and in the Amazonian region. In French Guiana, Le Bail et al. (2000) list 5 species of Harttiini including 1 Harttia , H. surinamensis , and 2 other species now assigned to Harttia : Cteniloricaria fowleri from the Oyapock drainage and Cteniloricaria maculata from the Maroni and Sinnamary drainages. Morphological differences between populations of H. surinamensis were noted. French Guiana specimens differ from specimens of the type locality by the absence of abdominal scutes. Later, Rapp Py-Daniel and Oliveira (2001) put Cteniloricaria in the synonymy of Harttia and describe a new species from the Approuague and Sinna - mary drainages in French Guiana without considering western populations. In the light of these recent works, a revision of the genus Harttia in French Guiana was clearly necessary in order to clarify the taxonomical position of all populations and species and to redefine their distribution. A morphological study was carried out on all Harttia species and populations from French Guiana and on the type material of H. surinamensis from Surinam. 28 continuous quantitative variables, 20 categorical quantitative variables, and 6 qualitative variables were noted for each specimen. After selection of the suitable variables, data were analysed with multivariate analysis. According to our results, the distribution of H. surinamensis may be restricted to the Suriname River drainage. Paratypes of H. surinamensis from the Maroni drainage (upper Tapanahoni, Surinam) are now assigned to H. guianensis , while those from the Coppename drainage may represent a new species. As noted by Le Bail et al ., H. fowleri is morphologically close to the H. guianensis , whereas H. maculata is very different. Populations from the Maroni and Mana drainages are assigned to H. guianensis and differences between populations of H. guianensis are emphasized. Specimens from the type locality (Approuague drainage) are deeper than those of all other populations. Specimens from the Sinnamary drainage are different considering meristic data. A practical key to the species of Harttia from French Guiana and Surinam studied in this work is proposed.